Clamping device for guiding workpiece to drill flange hole

The utility model discloses a clamping device for guiding a workpiece to drill a flange hole. The clamping device comprises a flange drilling template, a supporting mechanism and a locking piece. A convex ring is arranged in the middle of the flange drilling template, and 4-8 guide holes are distributed in the flange drilling template; the supporting mechanism comprises a connecting key, a threaded hole is formed in the middle of the connecting key, sliding grooves are formed in the two ends of the connecting key, supporting pieces are installed in the sliding grooves, and when the supporting pieces support an additionally-installed workpiece, the connecting key is transversely blocked above a convex ring in the middle of the flange drilling template; the locking piece comprises a T-shaped key, external threads are arranged at the vertical end of the T-shaped key, the T-shaped key can penetrate through a convex ring in the middle of the flange drilling template to be in threaded connection with a threaded hol